Insulated coil



Oct. 3, 1944. G. CAMILLI 2,359,544

INSULATED COIL Filed Nov. 28. 1942 V2 sheets-sheet 1 Oct. 3, 1944. G. cAMlLLl INSULATED COIL Filed Nov. 28, 1942 2 Sheets-Sheet 2 .fw d Oa/Wm 3fm em't V@ A n@ TLPWWH Patented Oct. 3, 1944 UNITED STATES PATENT OFFICE INSULATED COIL Guglielmo camini, Pittsfield, Mass., miglior to General Electric Company, a corporation o! New York Application November 28, 1942, Serial No. 467,225

9 Claims. (Cl. 175-362) a continuous conductor with one end of each of the layers being connected to the next inner layer and the opposite end being connected to the next outer layer. Thus, with the inner conductor layer connected to a relatively low voltage source or to ground and the outer conductor layer connected to the high voltage source, full voltage will be impressed between the inner and outer conductors. Furthermore, if the coil surrounds a core the high voltage end of the outer conductor layer will be adjacent the core which is usually at ground potential. It is, therefore, necessary not only suitably to insulate the outer conductor layer from the close core which is at ground potential but creepage and puncture must be prevented between the outer edges of the adjacent conductor layers.

It is, therefore, an object oi' my invention to insulate concentric layer around windings in an improved and eilicient manner.

Another object of my invention is to provide a coil having a plurality of concentric conductor layers with improved insulation.

A further object of my invention is to provide an improved method for insulating the various conductor layers of the layer wound coil.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawings, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and formine a part of this specification.

In the drawings Fig. 1 is a side elevation in partial section of a transformer having a winding which is provided with an embodiment of my invention; Fig. 2 is an enlarged sectional side elevation of a portion of the winding illustrated in Fig, 1; Fig. 3 is a sectional side elevation of a portion of a layer wound coil illustrating a modification of my invention; and Figs. 4, 5, 6, and 'l illustrate various steps in the manufacture of the coil illustrated in Fig. 2.

The illustrated embodiments of my invention include a plurality of concentric conductor layers with insulation between layers having a. width greater than the width of the conductor layers. The layer insulation may be of any Suitable type such as crepe paper so that the vextending ends of the layer insulation may be folded to lie adjacent the surface of the coil. Outer insulation is placed around the outer periphery of the coil vIl with ends extending beyond the outer ends of the coil, the ends of the outer insulation snugly overlying the folded ends of the layer insulation. A

plurality of layers of insulation may be provided around the periphery, these outer insulation layers interleaving the folded ends of the layers oi insulation between the conductor layers. The outer ends of the insulation may be folded in any suitable manner. However, I have found that rthese ends may be folded without the usual method of slitting to fold paper by immersing the ends in a suitable liquid such as water. When the crepe paper is wet the ends may be` folded so as to overlie the outer end of the coil without the necessity of tearing or slitting the paper. The paper ends may then be bound in this condition and heated so as to dry the paper and make it further snugly iit the outer surface of the winding.

Referring more particularly to Fig.'1 of the drawings, I have illustrated a transformer which has particular application as a high voltage instrument potential transformer. It is to be understood, however, that my improved insulated coil construction may be employed with any 80 other suitable electrical apparatus. The transformer in Fig. 1 includes an insulated winding I0 having coils I I and I2 which will be described in detail below. The winding I 0 surrounds a suitable core I3, the core and coils being enclosed in a suitable casing I4. A high voltage lead i5 is connected to one of the coils, such as II, the lead being insulated by suitable insulation I6. A bushing I'I surrounds the insulation i6, the bushing being supported on a cover I8 of the 0 tank I4. A suitable insulating iuid such as oil may be placed in the bushing and tank, an expansion chamber I9 being provided at the top of the bushing I1. A terminal 20 is provided for connection with the high voltage lead. The terner such as on the bushing II and the terminal may be connected to any other suitable electric apparatus or to a high voltage line. The inner layers of the coils II and I2 may be connected 59 together in any suitable manner such as described in my Patent 2,297,606, and a lead in- Y sulated in a bushing is provided for connection with the outer layer of the coil I2 similar to the lead I5 and bushing I1. The bushing for the coil I2 may be placed adjacent the bushing I'I and minal 20 may be supported in any suitable man- 2 attacca is not shown in Fig. 1 as it is directly behind the bushing I1, When the transformer' in Fig. 1 is employed as an instrument potential transformer the high voltage terminals including the terminal `2li may be connected across the lines, the potential of which is to be determined. A suitable low/voltage winding 2l may be provided which has terminals 22 and 28 which may be connected to any suitable electric apparatus. When the transformer as illustrated in Fig. 1 is employed as an instrument potential transformer the terminals 22 and 28 may be connected to a suitable potential measuring device.

Referring m'ore particularly to Fig. 2 of the drawings, I have illustrated in detail the coil Il which is insulated according to my invention. In Fig. 1 the winding l0 is shown as made up of two similar coils Il and l2, only one of which is shown in full in Fig. 2, butit is to be understood that my improved arrangement for insulating coils may be employed with either one or any suitable number of coaxial coils. The coil H as illustrated in Fig. 2 includes a plurality of concentric conductor layers connected in series. Thus the concentric layers are wound on any suitable spool or cylinder 25 by winding a first layer 26 including a plurality of turns on the spool 25. The winding is started from the right as is illustrated in Fig. 2 and after winding on the layer 28 a suitable layer of insulation 21 is put over the layer 28 in the conventional manner, A second conductor layer 28 is then wound on the insulation 21, the left hand end of the layer 26 being connected to the left hand end of the layer 28 by a continuous portion 28 of the conductor which forms the turns ofeach layer. Any suitable number of concentric conductor layers may then be superimposed one upon the other in this manner.

When applyingsuch concentric layer wound construction, as described above, to a relatively high potential it will be seen that a relatively high potential will be impressed between the outermost conductor layer and the innermost conductor layer. Furthermore, the outer surface of the winding is adjacent the core I8 which is usually connected to ground. It will be seen therefore that a relatively high voltage will be impressed between the outer surface of the winding and the core. It is therefore necessary to insulate the concentric conductor layers so as to prevent puncture of the outer insulation between the outer layer and ground, between the various conductor layers, and to prevent creepage between the ends of the conductor layers. Thus, after providing any suitable number of conductor layers similar to the layers 28 and 28, and in Fig. 2 I have illustrated four such conductor layers, including layers 28, 28, 88, and 8|, I provide an intervening layer of insulation 82 which is somewhat wider than the width of the conductor layers. The layer insulation 82 having a width wider than the width of the conductor layers may be applied in any suitable manner, such as illustrated in Fig. 4. Thus any number of layers of suitable insulation such as crepe paper are wound on the outer surface of the last conductor layer 8| from a web 88. Further in order to have the conductor on top of the insulation layer 82 so as to be available for winding a next concentric conductor layer 84, I wind a portion of a conductor 85 with the plurality of layers forming the insulation 82. After making about one turn of the layer insulation 82 the conductor 88 will be available for 'winding a. first turn 8B of the conductor layer 84. It will be understood that after having wound the web 88 to provide the insulation layer 82 the web may be' cut as is indicated by the line 81. By winding gthe conductor 85 with the web 88 a connection may be made between the conductor layers without cutting either the conductor or the insulation. The conductor layer 84l may then be wound upon the layer insulation 82 leaving the ends of the insulation extending beyond the ends of the adjacent conductor layers. Any suitable numbers of conductor layers may then be wound and insulated in the manner already described in relation to conductor layers 21, 28, 80. .and 8i, and in Fig. 2 I have shown four such conductor layers wound on the insulating layer 82. After winding the fourth conductor layer 88 I again wind on a second intervening insulating layer 88 having ends which extend beyond the ends of the conductor layer 88 to any suitable length. This insulating layer 88 may also be wound on the outer surface of the conductor layer 88 in the manner described above in relation to Fig. 4. This process of winding concentric layer wound coils with intervening insulating layers at any suitablev points which have ends extending beyond the ends of the conductor layers may be continued for any suitable number of layers, and in Fig. 2 it will be seen that I have illustrated a third set of four conductor layers indicated by the numeral 40 wound on the outer surface of the insulating layer 89 in the vmanner described above in connection with the conducting layers 21, 28, 88 and 8|. Another insulating layer 42 is then wound aroundI the group of conductor layers 48 in the manner described above in relation to Fig. 4 so that the ends extend beyond the ends of the adjacent conductor layers to any suitable amount. Another group of conductor layers 48 is then wound around the insulating layer 42 and the last turn 44 oi.' the outer conductor layer may be connected to the high voltage conductor terminal I5. The outer surface of the outer conductor layer may be provided with a suitable conducting member 45 which forms an electromagnetic shield for the winding, as is well known in the art.

In order to fold the outer extending ends of the various extending insulating layers I suitably wet the extending ends so that they may be folded without the necessity of splitting or tearing the ends. This may be accomplished in any suitable manner, such as by placing the ends of the coil in a vessel 50, as is illustrated in Fig. 5, which is partially filled with a suitable iluid 5I, such as water. The coil may then be placed again on the mandrel and outer ends 52 and 58 of the layer 42 may be folded toward the outer periphery of the coil around the ends of the outermost conductor layer and shield 45. The length of the ends 52 and I8 which extend beyond the ends of the conductor layer group 48 may be of any suitable length so that they will extend around the top of the shield 4I and meet at the top. .'I'he various sheets which make up the insulating layer 42 are of the same width and when the ends 52 and 58 are folded around a substantially V shaped opening will be formed. 'I'his may be filled up with suitable insulation 84, if desired. The coil is now ready to have a first outer layer of insulation, such as that indicated by the numeral 55 `in Fig. 2, wound around the outer peripheral surface of the coil. Referring tolilgitwillbeseenthatasheet 51 ofsuitable insulating material has an end 58 secured to the coil. The coil may then be rotated so that the sheet Il may be wound upon the partially completed coil. It will further be seen that the width of the sheet il is wider than the width of the coil so that the ends 59 will be folded inwardly coil. Then by providing suitable tension on the y web 51 as it is wound, the outer ends 59 will be made to iit snugly over the groups of ends of the conductor layers 43 and 40. After a suitable amount of insulation has been wound to form the outer insulating layer 55, the next insulating layer 39 may be folded around so that its ends 6D snugly fit around the edges 59 of the insulating layer 55. In order to make a smooth outer surface the space formed at the end of the end BU may be filled with suitable insulation Si. Another web of insulating material of suitable lwidth may then be wound on the coil so`as to form the next outer insulating covering G2 wound around the outer peripheral surface of the partially completed coil. It will be seen that this covering or layer 62 is of suitable width so that the ends 63 fold down until they are adjacent the insulating layer 32. 'Ihe layer 32 may then be folded up around the ends 5370i the insulating layer $2 and then a suitable web of insulating material wound around the coil so as to form an outer insulating covering or layer 66. The web forming the insulating layer 68, it will be seen, is suiiiciently wide` so that ends El snugly overlie the assembly adjacent the ends of the conductor layer 26. In order to hold the so folded insulating layers in this shape a few turns of tape lil may be wound around the coil and the coil may then be placed in'an oven so as to slowly dry the wet ends of the paper and cause them to shrink around the winding.

A so insulated winding may then be employed by itself in a transformer or a pair of such windings as illustrated in Figs. 1 and 2' may then be placed on a common insulating cylinder 80 and the space therebetween built upwith suitable insulation 8|. Insulating layers 82 and 83 may then be wound around the outer periphery of the coil having suitable width so that they will snugly t around the coil. These layers of insulation 82 and 83 may be placed around the coil in the .same manner as the various insulating layers described above have been wound around the outer peripheral surface of the coil. 1f it is desired, further insulation may be built up around the so insulated coil by winding 'a tape of insulating material through and around the coil so as to form the insulating layer 84.

In Fig. 3 I have illustrated a modification of my invention including intervening layers folded along the surface of the coil with insulation wound around the outer periphery with the edges snugly fitting over the folded ends of the intervening insulating layers, without interleaving the outer peripheral insulation and the intervening layer insulation as is done inI the construction illustrated in Fig. 2. In Fig. 3 I have illustrated a plurality cf groups of concentric conducting layers 9B, 9i, 82, and 93, which are wound similarly to the layers in Fig. 2. The coil is formed by first winding an insulating layer Se on a winding mandrel or suitable cylinder 95. The ends of the insulator 94 are sufficiently lcng so that they may be folded over and lie along the outer ends and the outer peripheral surface of the winding or outer conductor layer. Similarly intervening layers of insulation 96 are placed between the groups of layers 9B and Si. Also an insulating layer 81 is placed over the outer conducting layer of the group 9i, and insulating layer 98 is placed over the outer conducting layer of the group 92. The intervening insulating layers 94, 96, 97 and 98 may be of any suitable width so that they may be folded along the outer surface of the coil to any suitable degree. It will be seen with the construction in Fig. 3 that the extending ends of the various intervening insulating layers are sumciently long so that they may be made to overlap at the top of the coil. Thus, the outer intervening layer 98 has ends 99 and 100 which overlap a short distance. Also, the intervening layer 97 has ends lill and H12 which overlap and the end l0! is suiiiciently long so as to be folded over until it touches an end |93 of the layer 96. The insulating layer 96 has an opposite end i011 which folds a slight distance over the end i133. In order to make a smooth outer surface it is to be understood that suitable insulation H25 may be built up between the adjacent ends ofthe overlapping insulation. Finally the inner layer 9d has an end lS which is folded over and is adjacent the end i9?. The end 106 is sumciently long so that it cornes to theedge of the coil. It is to be understood that the various ends of the intervening insulating layers may he folded over in any suitable manner such as by wetting the ends before folding them over, according to the method which has already been described.

In order to insulate further the coil any suitable number of layer's or coverings of insulating material may be placed around the outer periphery of the coil. Thus in Fig. 3 I have illustrated two layers H0 and IH which are wound around the outer periphery of the coil andghave sufficient width so that the ends of the insulation may snugly overlie the sides of the coil. This insulation may also be Wound on the coil in the manner described above. If desired two such coils as have been described above in connection With Fig. 3 may be placed coaxially and a further layer H2 Aof insulation bound aroundthe outer periphery and over the outer ends thereof. 'Ihis composite coil may then have suitable insulation, indicated by the numeral H3, wound through and around the insulating coil to a suitable thickness.

In the construction described above in relation with Fig. 3 it will be seen that not only does the intervening insulating layers have sucient width so that their ends may .be folded until they overlap at the top of the coil, but further the overlappings of the adjacent layers are made to be staggered as is clearlyseen in Fig. 3. With such a construction the joint between adjacent ends will be covered by a relatively continuous port-ion of the insulation thus providing a maximum of insulating strength at the top of the coil.

In winding the various insulating layers which are placed between the concentric conductor layers as is illustrated in Fig. 4 it is desirable to employ a suitable flexible insulating material the ends of which may be stretched when it is desired to fold them over. It is to be understood, however., that if the material is sufficiently resillent when the web is wound around the coil it may be stretched while it is being wound. In order to prevent the stretching of the paper while it is being wound between the layers suitable reinforcing means may be provided on that portion of the web which overlies the coil. as illustrated in Fig. 7 let us assume that any suitable layer of insulation is being provided. The web |20 has ends which extend over the immediately inner coil and a suitable number of reinforcing strips III are placed on the web. These reinforcing strips are so placed that they -will surround the adjacent concentric conductor layers and leave unreinforced the ends which are to be folded over. 'I'he reinforcing strips may be made of any suitable material such as kraft paper or scotch cellulose tape.

In view of the foregoing it will be seen that I have provided an improved method for insulating concentric conductor layers by combining layer insulation which is folded around the ends with outer peripheral applied insulation which is folded over` the folded ends of the layer insulation. Thus. the foldedl ends of the layer insulation and the outer peripheral insulation may be interleaved or the outer peripheral insulation may be placed entirely around the folded ends of the interleaved insulation.

Although I have shown and described particular embodiments of my invention, I do not desire to be limited to the particular embodiments described, and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A coil for electrical induction apparatus including a plurality of concentric conductor layers, layer insulation between said conductor layers, and having ends extending beyond the ends of said conductor layers. said layer insulation ends being folded to lie adjacent the surface of said coil, and insulation around the outer peripheral surface of said coil, said outer peripheral insulation having a width greater than the width of said coiland having ends extending beyond the outer end of said conductor layers, said ends of said layer insulation being interleaved with said ends of said outer peripheral insulation.

2. A coil for an electrical induction apparatus including a plurality of concentric conductor layers, layer insulation between said conductor layers, said layer insulation having a width greater than the width of said coil and having ends extending beyond the ends of said conductor layers, and a plurality of layers of insulation around the outer peripheral surface of said coil, said outer peripheral insulation layers having a width greater than the width of said coil and having ends extending beyond the outer end of said conductor layers, said ends of said outer peripheral surface insulation layers being interleaved with said ends of said layer insulation.

3. A coil for an electrical induction apparatus including a plurality of concentric conductor layers, layer insulation between said conductor layers and having ends extending beyond the ends of said conductor layers, and insulation around the outer peripheral surface of said coil, said outer peripheral insulation having a width greater than the width of said coil and having ends extending beyond the outer ends of said Thus conductor layers. said ends of said layer insulation extending outwardly toward the outer periphery of said coil and adjacent the surface of the ends of said coil and said outer peripheral surface insulation extending inwardly adjacent the surface of the ends of said coil.

4. A coil for an electrical apparatus including a first layer of insulation,.a iirst conductor layer around said first layer of insulation, said nrst layer of insulation having a width greater than said first conductor layer andends folded toward the outer periphery of the coll adjacent the ends of said first conductor layer, a second conductor layer, and insulation around the outer peripheral surface of said second conductor layer, said outer insulation having a width greater than the width of said conductor layer. and the extending ends of said outer insulation snugly overlying the folded ends of said layer insulation. i

5. A coil including a first conductor layer, a second conductor layer around said nrst. a first insulating layer adjacent the inner periphery of said first conductor layer, a second insulating layer between said conductor layers, said insulating layers having ends extending beyond the outer ends of said conductor layers, said ends of said second insulating layer being folded over the ends oi' said second conductor layer, a third layer of insulation wound around the outer peripheral surface of said second conductor layer and having ends snugly overlying said ends of said,second insulating layer, said ends of said first insulating layer overlying said ends of said 'third outer peripheral insulation layer, and a fourth layer of insulation wound around said third outer peripheral insulation and having Y ends snugly overlying said first insulating layer.

6. A coll for an electrical induction apparatus including a plurality of concentric conductor layers, crepe paper insulation wound between said conductor layers and having ends extending beyond the ends of said conductor layers.' the creping of said paper running parallel with the axis of said coil so that said extending ends may be folded adjacent the ends of said coil, and reinforcing means on said crepe paper between the ends of said layers so as to Iprevent stretching of said paper as it is wound between said conductor layers.

7. A coil for an electrical induction apparatus including a plurality of concentric conductor layers, crepe paper insulation wound between said conductor layers and having ends extending beyond the ends of said conductor layers, the creping of saidv paper running parallel with the axis of said coil so that said extending ends may be folded adjacent the ends of said coil, reinforcing means on said crepe paper between the ends of said layers so as to prevent stretching. of said paper as it is wound between said conductor layers, and crepe paper insulation wound around the outer peripheral surface of said coil, said outer surface insulation having ends extending beyond the outer ends of said conductor layers, said ends of said layer insulation and said'outer peripheral surface insulation being folded adjacent the surface of the ends of said coil.

8. A coil for an electrical induction apparatus including a plurality of concentric conductor layers, layer insulation between conductor layers, said layer insulation having a width greater than the width of said conductor layers with ends extending adjacent the ends of said conductor layers, said ends of said layer insulation being overlapped around the outer peripheral surface of the outer of said concentric conductors.

9. A coil for an electrical induction apparatus including a plurality of concentric conductor layers, layer insulation between conductor layers, said layer insulation having a width greater than the Width of said conductor layers with ends extending adjacent the ends of conductor layers and around the outer peripheral surface of the outer of said conductor layers, and insulation around the outer of said conductors layers and having ends adjacent said ends of said layer insulation adjacent theends of said conductor layers.

GUGLIELMO CAMILLI. 

